The present invention relates to a method for processing a fluid containing a pollutant(s) (polluted fluid) to make the pollutants harmless, and more particularly to a method for processing a polluted fluid, suitable for making a pollutant present in a small amount in a large amount of fluid, or for making a specific pollutant present in the polluted fluid at a relatively low concentration coexisting with the other pollutants at a relatively high concentration.
An oxidizing treatment with ozone is known in the art as a method for processing a gas or water containing pollutants (polluted fluid). Ozone, which is self-decomposable and, thus, is unlikely to remain in the processed fluid so as to give detrimental effects to the human body, is expected to be used widely in future as a clean processing agent.
For performing treatment with ozone, an ozone-containing gas from an ozone generator (ozonizer) has been injected into a polluted fluid. However, the concentration of the pollutants in the polluted fluid is very low in general, with the result that a large proportion of ozone is decomposed before its contribution to the decomposition by oxidation of the pollutants. It follows that ozone fails to make the polluted fluid harmless at a high efficiency.
Recently, among various environmental pollutants contained in a polluted gas, dioxin becomes an issue of great concern, and it is desired to develop a method for effectively processing a polluted gas containing dioxin, such as an exhaust gas from a refuse incinerator. Dioxin can be decomposed by the oxidation with ozone. However, a large amount of the other harmful substances such as VOCs (volatile organic compounds), SOx and NOx are often contained in the exhaust gas from a refuse incinerator, in addition to dioxin and their total concentration amounts to 10 to 100 times the concentration of dioxin. Therefore, even if ozone is introduced into the dioxin-containing gas, ozone is consumed due to the reaction with the large amount of the other harmful substances, and can not contribute to the decomposition by the oxidation of dioxin.
Likewise, recently, the generation of malodor in various water systems such as a water-supply system or a sewage system, in particular, musty odor in a water purifying plant, due to 2-methylisoborneol (2-MIB) or diosmin mainly originating from microorganisms, also becomes an issue of great concern. Conventionally, a treatment with activated carbon is carried out to remove musty odor in these water system. However, the treatment with activated carbon is low in removal efficiency, must be renewed frequently, and is costly.
The malodorous components such as 2-MIB can be decomposed by the oxidation with ozone. However, the concentration of the malodorous components is very low in the water system, or a large amount of the other harmful substances such as COD (chemical oxygen demand) components are often contained in the water system, in addition to malodorous components, and their total concentration amounts to 10 to 100 times the concentration of malodorous component. Therefore, even if ozone is introduced into the malodorous component-containing water, ozone is decomposed due to contact with water, or consumed due to the reaction with a large amount of the other harmful substances such as COD components, and can not contribute to the decomposition by the oxidation of the malodorous components.
It is therefore an object of the present invention to provide a method for processing a polluted fluid containing pollutants to efficiently make the pollutants harmless by the treatment with ozone.
It is another object of the invention to provide a method for processing a polluted fluid containing a specific pollutant together with a large amount of the other harmful substances or pollutants to preferentially decompose the specific pollutant and make it harmless by the treatment with ozone.
These and other objects which will be become apparent from the following description are achieved according to the present invention by a method for processing a polluted fluid containing at least one pollutant, comprising the steps of passing the polluted fluid through an adsorbing layer containing a high-silica adsorbent capable of adsorbing both ozone and at least one pollutant to adsorb at least one pollutant on the adsorbent; and bringing ozone into contact with the adsorbing layer to oxidize and decompose the pollutant adsorbed on the adsorbent, while stopping the flow of the polluted fluid.
According to the present invention, there is further provided a method for processing a polluted fluid containing at least one pollutant, comprising the steps of providing at least one processing chamber containing an adsorbing layer comprising a high-silica adsorbent capable of adsorbing ozone and at least one pollutant; and effecting, in the processing chamber, a processing cycle including an adsorption phase in which the polluted fluid is passed through the adsorbing layer to adsorb at least one pollutant on the adsorbent and the fluid having passed through the adsorbing layer is discharged from the processing chamber, and a decomposition phase in which ozone is brought into contact with the adsorbing layer which has adsorbed the pollutant to oxidize and decompose the pollutant adsorbed on the adsorbent, while stopping the flow of the polluted fluid. In this case there can be provided a plurality of processing chambers each filled with the high-silica adsorbent, and at least one processing chamber can be subjected to the adsorption phase, while the other processing chamber is subjected to the decomposition phase.
In the present invention, the polluted fluid may contain a plurality of pollutants at least one of which can be preferentially adsorbed by the high-silica adsorbent.
In the present invention, the high-silica adsorbent is preferably selected from the group consisting of a high-silica pentacile zeolite, a dealumination faujasite, a mesoporous silicate and a mixture thereof.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.